Stiebel Eltron LWZ & LWA

Use cases

• Monitor outside, flow, and return temperatures on a live dashboard to verify ventilation system performance.
• Set room temperature and DHW setpoints remotely to adjust comfort levels without a site visit.
• Create an alert when a fault status register changes to detect ventilation failures early.
• Switch fan stages between day, night, party, and manual modes based on occupancy schedules.
• Track actual DHW temperature over time to verify hot water performance and identify efficiency drops.
• Compare HC1 and HC2 room temperatures to detect imbalances between heating circuits.

Installation

1. 1Install and configure the Stiebel Eltron ISG gateway according to the manufacturer instructions and connect it to the same local network as your ModbusCloud gateway.
2. 2Assign a static IP address to the ISG gateway and note the Modbus TCP port (default 502).
3. 3Connect your ModbusCloud gateway (MCG or MLP series) to the same network and ensure it can reach the ISG gateway IP address.
4. 4Import the Stiebel Eltron LWZ and LWA template from the ModbusCloud template library into your project.
5. 5Configure the connection in ModbusCloud by entering the ISG gateway IP address and port, and verify that register addresses use zero-based indexing.
6. 6Commission the template by checking live readings for outside temperature and operating status to confirm communication is working.

Things to watch for

01

Why are all temperature values showing as very large numbers?

Temperature registers use uint16 encoding with a scale factor. Verify that the template scaling is applied correctly. The outside temperature register is an exception and uses int16 encoding to support negative values.

02

Why does my ModbusCloud gateway not connect to the ISG?

Confirm that the ISG gateway and the ModbusCloud gateway are on the same network or have a routed path between them. Check that the ISG IP address and Modbus TCP port (default 502) are correctly entered in the template configuration.

03

Why do register addresses seem off by one compared to the Stiebel Eltron documentation?

This template uses zero-based addressing. A register documented as 1001 in the Stiebel Eltron manual corresponds to Modbus address 1000. Ensure your configuration does not add an additional offset.

04

Do I need a specific ISG firmware version for all registers to work?

Yes. Older ISG firmware may not expose all registers used in this template. Update the ISG to the latest firmware version available from Stiebel Eltron before commissioning.

Registers (23)

23 read / 11 write

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